1. Field of the Invention
The present invention relates to a semiconductor device which radiates heat and applies a substrate potential both from the rear surface of the semiconductor chip.
2. Description of the Related Art
In order to efficiently radiate heat generated from a semiconductor chip, the heat should be transmitted from the rear surface of the semiconductor chip, which is located opposite to the main surface on which a semiconductor element is provided. A semiconductor device having the structure in which heat is radiated from the rear surface of the semiconductor chip, is discussed in, for example, IEEE 1993 JAPAN IEMT SYMPOSIUM JUN. 9-11, 1993 KANAZAWA, JAPAN pp. 81-84. Tanaka et al., "MULTICHIP MODULE FOR 156 MB/S OPTICAL INTERFACE".
FIG. 1 is a diagram showing a conventional semiconductor device which radiates heat from the rear surface of the semiconductor chip. A semiconductor element is provided on the main surface (facing downward in FIG. 1) of a semiconductor chip 101, and a semiconductor chip mounting plate 103 which functions as a heat radiating plate is attached to the rear surface (facing upward in FIG. 1) via a buffer 102. The buffer 102 serves to reduce the stress applied to the semiconductor chip 101 and transmit the heat generated from the semiconductor chip 101 to the semiconductor chip mounting plate 103, and the buffer 102 is made of a material having a flexibility and a high heat conductivity. Bumps 104 are provided on the main surface of the semiconductor chip 101, which is attached to a conducting path forming member 105 via these bumps 104. On one surface of the conducting path forming member 105 which faces the semiconductor chip 101 and within the conducting path forming member 105 itself, conducting paths 107 are formed, and on the other surface, bumps 108 for connecting external terminals, which are electrically connected to these conducting paths 107, are provided. With this structure, a semiconductor element formed in the semiconductor chip 101 and the external-terminal-connection bumps 108 are electrically connected to each other. The semiconductor chip 101, the buffer 102, a portion of the semiconductor mounting plate 103, the bumps 104 and a portion of the conducting path forming member 105 are sealed by a package 106 made of a resin. The surface of the semiconductor chip mounting plate 103 and the surface of the conducting path forming member 105 on which the external-terminal-connection bump 108 are not covered by the package 106.
with the above-described structure, heat generated from the semiconductor chip 101 is propagated to the semiconductor chip mounting plate 103 via the buffer 102, and the heat is diffused from the exposed surface of the plate 103, which is not covered by the package 106, and radiating fin (not shown) provided on the exposed surface, thus achieving a highly efficient heat radiation.
In the case where a particular potential is applied to the semiconductor substrate, it is known that an electrode should be provided on the rear surface of a semiconductor chip. A semiconductor device in which the electrode of the rear surface is provided is discussed in, for example, IEEE 1993 JAPAN IEMT SYMPOSIUM JUN. 9-11, 1993 KANAZAWA, JAPAN pp. 176-177. Nakatsuka et al., "FINE PITCH AND HIGH LEAD COUNT MULTILAYER CERAMIC QFP. However, it is difficult to employ the above-described structure in which heat is radiated from the rear surface of a semiconductor chip and the structure in which an electrode is formed on the rear surface, at the same time. Thus, in the semiconductor device shown in FIG. 1, an electrode cannot be formed on the rear surface of the semiconductor chip 101, and therefore an electrode to be formed on the rear surface of the semiconductor chip 101, i.e. an electrode used for applying a substrate electrode, is formed in the main surface of the semiconductor chip 101. With such a structure, the size of the chip is increased, and this structure is disadvantageous to the production process of semiconductor devices.